1. Field of the Invention
The present invention relates to a common rail and a method of manufacturing the same, which is adapted to accumulate pressure of fuel pressurized by a high-pressure pump so that the high-pressure fuel is supplied by controlling an opening and closing valve from an injection nozzle to a combustion chamber, and more specifically to a device for connecting the common rail with a piping component comprised of a branch pipe, a supply pipe, a blank plug, a pressure sensor, a pressure regulating valve, or the like, and a method therefore.
2. Description of the Prior Arts
High pressurization has being practiced in order to reduce particulates and NOx from a diesel engine. However, as the pressure of fuel is raised higher, more difficulty is encountered in control of timing of a fuel injection pump and a fuel injection nozzle of a fuel injection apparatus, particularly the timing of beginning and ending of injection. To cope with this, a method is proposed that fuel is previously pressurized by a high-pressure pump to accumulate the pressure of the pressurized fuel while providing a mechanically or electrically controlled opening and closing valve to an injection nozzle so that high-pressure fuel is supplied to a combustion chamber by controlling the opening and closing valve. A relatively thick walled metal pipe for the pressure accumulating chamber, in this case, is referred to as a common rail.
In the conventional common rail of this kind, as shown in FIG. 4, a thick wall pipe 1 for accumulating the pressure of high-pressure fuel has an inner peripheral surface formed with a thread 1b in which screw-fixed is a joint 2 having a thread provided in an outer peripheral surface at opposite ends of a cylindrical wall thereof. On the other hand, to the joint 2 is connected a piping component 3 comprised of a branch pipe or a supply pipe that has therein a flow passage for communication of high-pressure fuel to a high-pressure pump, a combustion chamber, or the like by means of a fastening nut 5 through a sleeve washer 4. Otherwise, as shown in FIG. 5, a fastening nut 5 is fixed by screwing through a ball 6 onto the thread 1a formed in the outer peripheral surface of the thick wall pipe 1 to form a piping component comprising a blank plug. Otherwise, as shown in FIG. 6, for connecting with a piping component 3 comprised of a pressure sensor, a pressure regulating valve, a flow limiter, or the like, connection is made by screwing a housing 5' integral with the piping component 3 or a separate fastening nut onto the thread 1a formed at the end of the thick wall pipe 1 so that communication is done to the inside of the thick wall pipe 1 by means of a cable 8 through a reinforcing coil 7.
With the conventional common rail, however, the number of parts is increased because of the necessity of a separate joint 2 for connection with a piping component such as a branch pipe or a supply pipe. Furthermore, since the structure is to connect both the thick wall pipe 1 and the piping component 3 to the joint 2, screwing portions increases in number and assembling operation becomes complicate, requiring full attention to leakage at these points. Furthermore, for connecting with a piping component such as a blank plug, a pressure sensor, a pressure regulating valve, a flow limiter, or the like, the fastening nut becomes large in size, and the area of screwing portion increases, thereby requiring sufficient attention to leakage. Furthermore, the requirement of weight-lightening for components has been not met.